1. Technical Field
The present invention relates to an image forming apparatus that fixes an unfixed toner image formed on a recording material using electrophotography, electrostatic recording, or the like by heating and fusing, and a fixing device using an endless belt member at the time of fixing and an image forming apparatus using the device.
2. Related Art
Conventionally, in an image forming apparatus such as a copier and printer utilizing electrophotography or the like, as a fixing method for turning an unfixed toner image formed and carried on a recording material into a permanent image by the intermediate transfer method or direct transfer method, a fixing device of type using heat and pressure rolls has been used.
In the type using heat and pressure rolls, a heat roll (fixing roll) and a pressure roll are rotated in pressure contact with respect to each other. The recording material carrying the unfixed toner image is passed through the fixing nip region as the pressure contact part with each other of the pair of rolls. The toner image is heated, pressurized, and fixed on the recording material.
Recently, a method of outputting a digital image in the same finishing as that of a photo print in an image forming apparatus has been proposed.
On the other hand, in character output, a less glossy (low-gloss) image is preferable for better viewing of characters by human eyes. Accordingly, when not only photo printing but also conventional outputting of characters principally is performed, a technology of selectively using two fixing devices, one for fixing as a low-gloss image and another for fixing as a high-gloss image according to need, has been proposed.
As the fixing device for outputting a high-gloss print, an unfixed toner image on a recording material is brought into contact with a fixing belt surface in contact with the fixing roll side and is heated, pressurized, and fused. The fused toner image is cooled to predetermined temperature while the fixing belt is in contact with the recording material, and then, the recording material is detached from the fixing belt. Thereby, the toner image surface can be transferred to the smooth surface property of the fixing belt surface, and consequently, a high-gloss image is obtained.